Printed circuit boards are often used in many applications to operate or run electronic devices. Due the circuitry on such printed circuit boards and the amount of energy used to operate them, these printed circuit boards can often generate a large amount of heat. To improve the operability, the printed circuit boards are often attached to a device or substrate that can facilitate dissipation of the heat away from the printed circuit boards. By removing the heat, the printed circuit boards can operate at lower temperatures. By operating at lower temperatures, the components of the printed circuit boards can more readily function in their intended manner. In some cases, the lower operating temperatures can allow for the use of smaller components on the printed circuit boards to permit the printed circuit boards to be offered in smaller sizes.
The devices or substrates that are attached to the printed circuit boards, hereinafter referred to as heat sinks or heat sink structures, often directly or indirectly contact the printed circuit boards and draw heat away from the printed circuit boards. The heat sinks can be made of materials that are thermally conductive to more readily pull or conduct heat away from the printed circuit boards. Additionally, the size and shape of the heat sinks can improve heat dissipation from the printed circuit boards.
The use of heat sinks in conjunction with electrical boards, such as printed circuit boards, can be especially advantageous when the printed circuit board is being used in a lighting fixture, such as a light-emitting diode fixture, that tends to generate even more heat than just a printed circuit board alone. Various implementations of light-emitting diode lighting fixtures are becoming available in the marketplace to fill a wide range of applications. Such different lighting applications in which light-emitting diodes can be used include domestic lighting, billboard and display lighting, automotive and bicycle lighting, emergency lighting, traffic and railway lighting, and floodlight and flashlight use. Light-emitting diodes are smaller than incandescent bulbs and use less energy. In addition, light-emitting diodes have a longer life than standard incandescent light bulbs. Accordingly, the use of light-emitting diodes in lighting applications can provide significant energy savings, increased lamp life, smaller lamp size, and flexibility in the design. For these reasons, lighting manufacturers are increasingly interested in unique lighting fixtures incorporating light-emitting diodes that may also have appeal to their intended customers. For the light-emitting diode fixtures to operate properly and to provide improved lighting, heat needs to be dissipated from the light-emitting diode.
As stated above, good direct or indirect contact between the heat sink and printed circuit boards is desired to increase the effectiveness of heat dissipation from the printed circuit boards, especially those that include light-emitting diodes. Typically, printed circuit boards are attached to the heat sinks by screws or the like. The screws have a tendency to unscrew or back out, which, in turn, permits the amount of contact between the printed circuit board and the heat sink to decrease. This results in a lessening of the thermal transfer to the heat sink. Additionally, depending on the force used to drive the screws into the heat sink, bowing of the printed circuit board can also decrease the contact between the printed circuit board and the heat sink. For example, if one or more of the screws are fastened to tightly, the clamping force at the pressure point where the screw contacts the printed circuit board can cause the printed circuit board to bend upwardly.
Further, when using screws to hold printed circuit boards to heat sinks, the ability to remove and reattach the printed circuit board to the heat sink while still optimizing thermal transfer after reattachment is often lessened. Once a screw is driven into the heat sink, the frictional hold between the screw and the heat sink is often lessened if the screw is removed and reinserted into the same hold. This can lead to a tendency of the screws to loosen or back out.
While using heat sinks in conjunction with printed circuit boards can improve heat dissipation, providing good contact between the printed circuit boards and the heat sinks can be important. Good clamp forces between the heat sinks and the printed circuit boards can improve the contact between them. Additionally, the ability to quickly attach the printed circuit board to the heat sink in a repeatable fashion is desirable to improving related manufacturing. Further, the ability to remove and reattach the printed circuit boards while still providing good clamping force and contact between the printed circuit board and the heat sink is desired.